This invention relates to health management, in particular, to weight control.
Good health and weight control are of considerable interest to a large number of people. Many people engage in conventional weight loss schemes, usually based on a restricted calorie diet. Physical activity may be included in a weight control program. A calorie management system allows a person to compare their caloric expenditure, comprising resting metabolic rate (RMR) and activity-related caloric expenditure, to their caloric intake in the form of food and beverages. Caloric expenditure has two components, a larger contribution related to resting metabolic processes, and a smaller contribution related to the energy expended in physical activity. We may say that total energy expenditure (TEE) is the sum of resting energy expenditure (REE, a product of resting metabolic rate and the time-period of interest) and activity related energy expenditure (AEE), i.e.:
TEE=REE+AEE
Caloric balance is defined in terms of the difference between TEE and the caloric intake of the person.
In some prior systems of weight control, a person""s RMR has been estimated using the Harris-Benedict equation, which relates RMR to body height, weight, age, and gender. This equation is well known to those skilled in the diet and nutrition arts (e.g. Williams, certificate of correction to U.S. Pat. No. 5,704,350, and Krause and Mahon, xe2x80x9cFood Nutrition and Diet Therapyxe2x80x9d). Alternatively, charts and tables, usually based on the Harris-Benedict equation, may be used. Additional demographic factors and body fat percentage may be included to improve the estimate of RMR.
It is important to realize that the values of RMR obtained using equations, tables, charts and the like, only provide an estimated RMR value for an average person. A person with a given height, weight, or other physical parameter (such as may be entered into the Harris-Benedict equation or modified equation) may have an actual RMR that is significantly different from the estimate. Actual RMR values for individuals within a group of apparently similar persons will fall on a distribution around the estimated RMR value for an average person. This distribution leads to errors in the caloric needs calculated for a person in a weight control program.
Additionally, there is an even more serious inadequacy in conventional weight control programs. The RMR of a person changes unpredictably as a weight control program progresses. A person may respond to the perceived starvation conditions through a significant drop in RMR. As a consequence, such a person may even gain weight on a reduced calorie diet if their caloric intake required to maintain a given weight falls below the reduced value prescribed by the diet. This is an unsatisfactory outcome to a weight control program. Other people may suffer no fall in metabolic rate during the restricted calorie diet. If the weight control program contains an exercise component, the resting metabolic rate of a person may even increase during the program. The Harris-Benedict equation predicts that resting metabolism will fall as body weight is lost, but is not intended to predict the actual response of a person""s resting metabolic rate to a weight control program. Hence, estimating the resting metabolic rate of a person using an equation may lead to large errors in calculating the caloric needs and activity levels required for an effective weight control program. Hence, an improved weight control method which accurately compensates for changes in metabolic rate over time will be of great value.
RMR can be determined using an indirect calorimeter. Conventional devices are large, expensive, and difficult to use so that expert assistance is essential. A person will need to report to a specific location, such as a hospital, for use of a conventional indirect calorimeter. There is considerable difficulty and expense associated with conventional indirect calorimeter use, so that conventional weight loss programs do not monitor the RMR of the person in the program, but rather rely on an estimate such as provided by the Harris Benedict equation.
A very large number of weight loss approaches have been proposed, all of which suffer from the above discussed shortcomings. For example, in U.S. Pat. No. 5,704,350, Williams describes a nutritional microcomputer and method of use in a weight control program. A hand-held device is described which enables a diet log to be recorded, activity levels to be recorded, and diet goals to be set. The Harris Benedict equation is used to calculate the user""s daily caloric expenditure. Hence this device and method fails to take into account the change in RMR at the onset of a diet.
In U.S. Pat. No. 5,673,691 to Abrams et al. describe an apparatus to control weight, in which caloric intake levels are adjusted on the basis of changes in the user""s body weight. The actual metabolic rate of the user is not determined in the described method of using this device.
In U.S. Pat. No. 4,951,197, Mellinger describes a diet method in which caloric expenditure is calculated from the weight of the person. Individual variations in RMR, and RMR changes during a diet, are not taken into account.
In U.S. Pat. No. 5,890,128, Diaz et al. describe a hand-held calorie computer for use in a weight control program. For weight loss, caloric intake is decreased gradually so as to hopefully avoid abrupt changes in the user""s metabolic rate. However, this is not as effective as actually measuring the user""s metabolic rate and compensating for changes, as described in embodiments of the present invention.
In U.S. Pat. No. 5,705,735, Acorn describes monitoring the oxygen consumption and carbon dioxide production of a patient on a ventilator, and using the data to assess nutritional requirements. This apparatus not intended to provide information to the patient, but rather to a health professional in attendance, and is not convenient for use in a weight control program.
In U.S. Pat. No. 5,989,188, Birkhoelzer et al. describe the use of indirect calorimetrics in determining the energy balance of a living subject. However, Birkhoelzer et al. do not envision the problematical effects of metabolic change caused by a weight control program on predicting the outcome of the weight control program. They do not describe a weight control program in which the RMR of the subject is monitored through the course of the program, and do not describe how changes in RMR may be used to modify the recommended caloric intake, activity levels, and/or target goals of a weight control program.
Recently, James R. Mault, invented a low-cost, hand-held, portable indirect calorimeter, referred to as a Gas Exchange Monitor (GEM). This device allows accurate measurement of resting metabolic rate (RMR).
The inventor, James R. Mault, has carried out RMR measurements of persons in a weight control program, and found significant decreases in RMR which cannot be accounted for by weight loss using the Harris-Benedict equation.
The present invention accordingly overcomes the deficiencies of the prior art by measuring the resting metabolic rate (RMR) of a person at intervals, and modifying the RMR component of caloric balance on a dynamic basis to compensate for changes in metabolism which occur during weight control, particularly weight loss.
In the improved weight control program described herein, an indirect calorimeter is used to monitor the RMR of a person at intervals. The RMR values are used to modify the caloric intake and/or activity levels recommended in the weight control program.
The GEM allows direct measurement (not estimates) of a person""s RMR at intervals as a person""s metabolism changes as a result of a weight control program. RMR changes may be accurately tracked over the course of a weight loss program. RMR may be measured at more frequent intervals (for example, once every 1-5 days) at the start of a weight control program, when metabolism changes may be more rapid. The measurement intervals may be lengthened (for example to every 1-4 weeks) if the person""s RMR settles down to an approximately constant value in the course of a weight control program.
In a conventional weight loss program, a person will often become discouraged due to small or non-existent actual weight losses. This is often due to a failure to take RMR changes into account. The present invention allows a person to intelligently navigate a weight control program. Caloric intake may be reduced, activity levels increased, or weight loss expectations may be modified to take into account the changing value of RMR.
In one embodiment of the present invention, a person is provided with a portable computing device, such as a personal digital assistant, with software which enables the device to function as a caloric intake calculator, a caloric expenditure calculator, and a caloric balance calculator. A body weight target may be set, and the initial RMR value used to suggest a caloric intake level and activity level by which the target weight may be achieved in a reasonable time. Soon after the start of the weight control program, the person may be prompted or otherwise reminded to re-determine their RMR level. RMR may change significantly at the beginning of a weight control program. Any significant changes in RMR may be used to re-calculate a reasonable balance of caloric intake, caloric expenditure, and time needed to reach a certain body weight goal. The RMR of the person is measured at intervals through the duration of the weight control program, so as to revise the parameters of the program in a manner consistent with a successful outcome.